A light-emitting diode (LED) includes a PN junction. When a suitable voltage is applied to the light emitting diode, holes injected from a P region into an N region and electrons injected from the N region into the P region are recombined within a few micrometers near the PN junction to generate spontaneous radiation fluorescence (i.e., electroluminescence). Different semiconductor materials have different energy states for electrons and holes. The more energy is released when the electrons and the holes are recombined, the shorter a wavelength of the emitted light is.
As compared with an incandescent lamp, a LED lamp has many advantages, including but not limited to, lower energy consumption, a longer service life, higher reliability, a smaller size and a faster switching speed. The LED lamp is applied in a wide range, such as flight lighting, automobile headlights, advertising lighting and traffic signal displays and so on.